There are many braces for the protection, orthosis, and rehabilitation of limb joints in the human body. Such braces are diverse and may be used for a variety of purposes, which include: protecting against injury due, in particular, to transverse impact; rigidly limiting or restricting the normal range of motion; providing joint control due to instability; and assisting in the rehabilitation and mobilization of the joint. Generally, these braces are most effective in joint orthosis when the normal motion of a joint on a human limb is duplicated or accommodated by the brace, without restriction in order to minimize or avoid undue stress or strain within the joint. Accordingly, braces are most readily applied to synovial joints and are predominantly of the hinge variety. The joints in such braces often provide articulated motion by any one of many means such as, for example, single axis revolutes, bipivotal hinges, cam actuations, or "free form" controls furnished by multi-directional, flexible members.
Numerous U.S. patents illustrate a variety of brace joint designs and their unique functionality as related and applied to a specific medical application. For example, each of the U.S. Pat. Nos. 4,817,588 and 4,982,732 discloses a single axis hinged brace joint for injury recovery or limited post-operative restraint which include an adjustable, angular range of motion by means of flexion and extension stops that may be locked into place. In addition, the U.S. Pat. No. 4,982,732 discloses a keyed lock which prevents tampering with the brace joints.
U.S. Pat. Nos. 4,688,559 and 5,018,514 disclose a hinged and polycentric joint, respectively, which are designed to duplicate the more complex rolling and sliding behavior of the human knee during flexion and extension while simultaneously providing joint stability and limiting the forces of variable magnitudes to prevent abnormal rotations. Additionally, the '559 patent employs a tension cable and cam surfaces which provide the patient with a means for aligning and fixing the joint.
U.S. Pat. No. 4,100,918 discloses a dynamic knee extension assist for use by paraplegics or patients without adequate muscular structure and includes an elongated plastic cord with means for making tension adjustments. Moreover, the '918 brace provides a controlled knee for assistance, particularly in rising from and descending into a sitting position. Likewise, a similar concept for a knee and elbow brace joint is described in one of the embodiments of U.S. Pat. No. 4,433,679. In the '679 patent, several brace joint designs are disclosed for providing stabilization and rehabilitation for the knee or elbow.
U.S. Pat. No. 4,838,251 discloses a dynamic knee brace which utilizes an elastic member as a resilient return means and involves a method for working muscles which, in part, allows the patient to sit normally. The elastic member described in the '251 patent is eccentrically located with respect to the joint hinge which provides a moment about the pivot when the elastic member is in tension due to a flexion of the knee. Essentially, the joint function, which is about the same as the joint function shown in the '251 patent, is disclosed in U.S. Pat. No. 4,657,000 wherein an adjustable splint includes a compression spring that may be axially preloaded against a cam surface to provide an eccentrically applied force.
Although the aforementioned U.S. patents illustrate a variety of joint designs for braces and splints, there are problems associated with their designs. For example, the known brace joints have limited functionality. Specifically, the known joint designs either include means for adjusting the tension force or the range of angular motion within the splints and braces.
Accordingly, an object of the present invention is to provide a new and improved compact dynamic brace joint design for use in orthotic devices which overcomes the above-described design limitations. In particular, an object is to provide a brace joint that includes both a quantifiable continuous force and an incrementally adjustable range of angular motion that is controlled by flexion and extension limits.